[jira] [Created] (FLINK-16920) Flink UI cancel uses an undocumented rest api and uses GET rather than a mutating HTTP method

["John Lonergan (Jira)" <ji...@apache.org>]

John Lonergan created FLINK-16920:
-------------------------------------

             Summary: Flink UI cancel uses an undocumented rest api and uses GET rather than a mutating HTTP method
                 Key: FLINK-16920
                 URL: https://issues.apache.org/jira/browse/FLINK-16920
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Web Frontend
    Affects Versions: 1.10.0
            Reporter: John Lonergan


We were trying to build proxy that excluded all mutating operations and the documented rest API indicates that all mutating ops are always PUT/POST/PATCH etc and never GET.

However, then we took a look at the "cancel" feature in the UI and it uses an undocumented API that violates good REST practice by mutating on a GET. 

The UI contains this comment ....

https://github.com/apache/flink/blob/eb489cc2f7e01fa43cae1bf2106fc30f0cf829fb/flink-runtime-web/web-dashboard/src/app/services/job.service.ts#L75

```
/**
   * Uses the non REST-compliant GET yarn-cancel handler which is available in addition to the
   * proper BASE_URL + "jobs/" + jobid + "?mode=cancel"
   * @param jobId
   */
  cancelJob(jobId: string) {
    return this.httpClient.get(`${BASE_URL}/jobs/${jobId}/yarn-cancel`);
  }
```

Why is this bending necessary?
Why not use a POST or other mutating method?
Why not use a documented API?

This kind of thing makes it difficult to trust the product.

Any ideas?


==

Suggestion ... 

There exists "web.submit.enabled" to turn off /jar features
What would also be useful is "web.cancel.enabled" to turn off the UI button and also the servicve endpoint.



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